The Beosystem 2500 (and 2300) does not have masterlink, but you are right they can convert to masterlink with the use of the 1611 converter connected to the AUX socket of the Beosystem

And yes a 1614 can not be used in this scenario

Thought so (on both counts), but needed to check, so thanks for confirming. Seems a shame that those models don't have great multiroom capability.  You can't use MCL because they don't have the speaker sockets for that, and you can't use link room Beolabs without 1a 1611.  I understand that you can also use a Beolink Passive connected via Powerlink (instead of ML), and then connect passive speakers, but the person who asked me this question specifically wanted to use a Beolab 2000 with their Beosystem 2500, so I guess that's not an option for them.

For that use case the 1611 is the correct option. it is possible to use the Beosystem 2500 with MCL by use of a Beolink Passive or ML-MCL converter. It connects to the Beosystem with powerlink and converts to MCL